1. Field of the Invention
This invention relates generally to apparatuses and processes for the dehydration of water bearing gases (such as methane), and, more particularly to an organic emissions elimination apparatus and process for same for use in substantially eliminating the emission of potentially harmful organic constituents, such as benzene, toluene and xylene ("BTX") into the ambient environment during the dehydration of such gases.
2. Background Art
Dehydration of water bearing gas (such as natural gas) has been known in the art for many years. In addition, inasmuch as such gas typically contains trace amounts of potentially harmful organic constituents (such as BTX), the prior art has addressed concerns relative to the emission of such constituents into the ambient environment, during the dehydration process.
Indeed, in some of such prior art, the water bearing gas is forced into a membrane module either under the natural pressure of the gas, or, alternatively, through the use of a compressor, or the like. The membrane module includes a membrane which is substantially impermeable to the BTX (which may be found within the water bearing gas), while being substantially permeable to the water vapor, and, somewhat permeable to the gas itself. Accordingly, the "permeate stream," which will result within the membrane will typically comprise water vapor and some "lost" gas (which has permeated the membrane). This permeate stream is then discharged from the membrane module and into the ambient environment. However, the gas which has not permeated the membrane (the "dehydrated gas"), and the BTX, are discharged from the membrane module to a point of use by conventional gas burning equipment. Although some of the "lost" gas included in the permeate stream can be separated from the water vapor prior to discharge into the ambient ,environment, and then reintroduced into the membrane module (through conventional regeneration equipment), the capital cost of such equipment necessary for such reintroduction is too expensive to be practical.
Additional prior art dehydration devices and/or methods have alternatively utilized a water absorbing material, such as triethylene glycol ("glycol") as a dehydration agent--without the use, or cooperation with, a membrane or membrane module. Indeed, in such prior art devices and/or methods, the water bearing gas, and the glycol, are introduced into a first chamber. As the water bearing gas and the glycol come into contact with each other, the water vapor in the gas, negligible amounts of the gas itself, as well as some of the BTX, will be absorbed by the glycol. The non-absorbed gas (the "dehydrated" gas) will then be discharged from the first chamber toward a point of use by conventional gas using equipment.
The "absorbed stream" in the first chamber (which includes the glycol, water vapor and BTX) will be transferred to a regenerator where the glycol will be separated from the water and the BTX, and then the glycol will be reintroduced back into the first chamber. The remaining water vapor, and unfortunately, the potentially harmful BTX (both of which have been separated from the glycol) will be either directly, or indirectly, emitted into the ambient environment.